Telegraph system



JaxLlS, 1938. c. E. LoMAx TELEGRAPH SYSVTEM Filed Nov. 7, 1935 1N VEN TOR. CLA/2eme E. Lon/Ax BY ZM A TTORNEY.

Patented Jan. 18, 1938 UNITED STATES PATENT OFFICE 2,106,011 l TELEGRAPH SYSTEM Clarence E. Lomax, lOak Park, Ill., assignerl to 'Associated Electric Laboratories, Inc.,v Chicago,

The present invention relates to telegraph systems in general, but is concerned more particuj larly with a telegraph system in which specialsignals are required toy b e transmitted over a tele'- graph line to one or more signal stations located along such line. 7

' The Aobject ofthe invention is the' production of a new and improved" oircuit arrangement'for preventing theselective switches-'in "thesignal stations from operating needlessly 'responsive to' telegraph signals, thereby effecting a considerable saving in wear andY tear on the lselectors at the signal stations;

General description The invention is directed toward the vsolution of the problem that ariseswhen one or more signal stationsv are located along the route of a telegraph line extending between a telegraph transmitting station and a telegraph receiving'station. It is desirable to permi'tthe attendant at a desired one of the signalA stations to be signalled to perform a prearranged operation, such as teniporarily opening the line for test purposes; applying an artificial leakage shunt between the line and earth; removing ar previously applied artificial lshunt from between the lines and earth; and so forth. Previously, the desired signalling operations have been carried out by associating Va selector with a telegraph line'at each of they intermediate signal stations, and permitting the selector to be controlled over the line by" all`of the signals, telegraphic or otherwise, the selector being arranged so that it selects and completes a selected signal circuit only in the event that special: selecting signals diifering somewhat from' the telegraphic signals are transmitted over the line. While'this'arr'angementhas proven to be workable, the lselectors used wear out abnormally fast becausetheyrespond to the telegraph signals as well as to the special signals which are intended to bring about their operation.` This situation will be appreciated more fully when it is recalled that telegraph signals may be transmitted almost continuously for hours at aV time' over a busy telegraph line, while the special signals may be transmitted 'for'onlya'few seconds at a time and at'i'elatively rare intervals, perhaps not oftener' 50 than von the order cfa dozen'or so'timesa day.I

' An arrangeinent has therefore been devised for placing the signal selectors under the control of the telegraph line only responsive to`a special' sig'- nal "notl encountered' in the routine transmission of telegraph messages. Afeature'of the arrangement is that as soon as a selector has been oper,- ated completely "t make a selection itis automatically removed fro'munder the controlof the telegraph line:

Ithas been found convenient to use a prolonged opening of the lineas vthe special signal which indicatesthat selecting signals, as contrasted with telegraphic signals, are about to be transmitted and to 'arrange the relay apparatus which controls I the signalV selectors sov that signals 'transmitted over the telegraph linedo not reach the signal selectors unless precededby the prolonged opening of the line above referred to.

Referring now to thesngle iigure of the accompanying drawing, a telegraph transmitter I i'si'ndicat'ed dia'grammatically as interconnected by 'telegraph 'line 5 with telegraph receiver 2, locatedV at 'the distant 'end 'of the telegraph line. Two signal stations, A and'B, are shown along thetelegraphA line.

The"`Strowger selector SI is shown station A, andthe similar Strowger selector S2 is indicated at signal station B. Test panel 6 is inserted inthe line 5 at station A, while test panel 'l is inserted inthe. line at signal station B. It

at a signal r;

is at trese'test panels thatthe attendant may peri form Voperations such asset forthhereinbefore, when he is signalled to do so.

The normally closed push-button 4 is inserted in the line 5 to produce the prolonged bre-ak in theline which 'signifies'that selecting signals, as i contrasted with telegraph" signals, are about to be sent.' The calling device CD is preferably of the'usual iinger-hole-dial" type commonly used in automatic telephone systems 'to control'the operation of the automatic' switches. This calling device has the normally closed impulse contacts (as shown) connected directly in series with the telegraph line .for the purpose of transmitting 'desired predetermined series of interruptions in` the line when the calling device is turned in f t theusual manner and allowed to return to normal position.

`At signal station A, the Strowger selector Sl is of a' type Well known to those versed in the art o'f automatic switching. This selector has the usual doublmember wiper 38 mounted on a vertically movable and rotatable' shaft (not shown) so that it can be brought into operative relation with any desired one ofthe contacts in theiillustrated bank 39L arranged in ten horizontal rows or levels with ten contacts in each level. Only a few of the bank contacts are' shown for illustrative purposes. The vertical magnet3l is the'one which raises Ordinarily, the contact bank is the wiper 38 opposite the desired level of bank contacts; rotary magnet 32 is the one which rotates it over the selected level until it reaches the desired contact; and release magnet 33 is the one which brings about the restoration of the wiper 38 to its normal position when the release magnet is energized.

The usual conventional showing of the various relays ofthe selector Sl is made. It may'be pointed out that the illustration of release relay 22 indicates that this relay has a copper sleeve placed over the core thereof underneath the winding in order to render the relay slow-releasing by virtue of the magnetic eifect produced by the circulating current in the copper sleeve; relay 24 has a. copper collar encircling the core on the armature end thereof, as indicated by the solid black upper portion of the relay, so as to render the relay slow in operating responsive to a closure of its circuit; relay 25 has a copper collar placed around the core at the'yoke end thereof, whereby the relay is rendered slow in releasing, although it is not as slow in operating as one which has a copper collar on the armature end; and relays 25 and 2l are each provided with a conducting sleeve as explained in connection with release relay 22 so as to render them sloW releasing. The oli-normal contacts 34, 35, and 36 are mounted on the switch in the usual manner so as to move to alternate position when the wiper of the switch is moved from its normal position. l

Detailed descriptionr The disclosure having been described generally, a detailed description of the operation of the apparatus shown will now be given. For this purpose, it will first be explained how the relays 2| to 23 interact during the transmission of telegraph signals to prevent a response of the selector SI, it being understood that a similar arrangement is provided at the selector S2.

Relay' action during telegraphing Normally, the illustrated circuit over the telegraph line 5 is closed and current is flowing thereover. Relay 2| of the Strowger selector VSI is therefore in an operated position as shown in the drawing. During the transmission of a telegraph signal the circuit is successively opened and closed at the transmitter for variable lengths of time. If the usual Morse telegraph transmission is used, the well known dots and dashes are transmitted over the line, while if the'Baudout code system of transmission is employed (as in printing telegraphy) the signals are sent in coded time relationship, and the length and spacing of the openings inthe line are more variable.

When lineA relay 2| restores during signalling, it closes a circuit through contacts of cut-in re lay 25 through the resistor 30 to the negative, ungrounded pole of the local battery used at signal station A, thereby shunting the winding of the slow-acting release relay 22. Relay 22 is slow in restoring because of the circulating current flowing through the conducting sleeve previously mentioned and because of the additional circu-V lating current which flows'through its short circuited winding, both actions contributing to retard the decay of the established magnetic flux. As relays of this type are ordinarily constructed, the relay 22 may be expected to remain operated during a large fraction of a lsecond after it has become short circuited. By this arrangement, during much of the time of the transmission of signals, relay 22 does not restore because relay 2| is quickly reoperated, and the currentflow is thereupon reestablished through the winding of relay 22 from the resistor 30. Now it happens occasionally in telegraphic transmission that the open-line period exceeds the release time of relay 22, in which case line relay 2| is restored for a suicientlength of time to result in the restoration of release" relay 22. `Wherrrelay 22 restores, it operates the timer relay`23 which closes a circuit for the slow-operating locking relay 24 through the Weighted-spring contact associated with the armature of relay 23. The weight 31 is attached to the contact spring associated with the armature of relay 23 to cause the contact spring to Vvibrate rather vigorously for a time after the Contact is struckby the armature. Relay 24, by design and adjustment is sufficiently slow in operating that it does not actuate its armature until the vibration of the contact has substantially ceased. This period may conveniently be adjusted at about three seconds in order to insure that relay 24 does not operate until line relay 2| has been restored for a period of at least three seconds. Since the line is never opened for a time as long as this in the regular transmission of telegraph messages, timer relay 23 is always restored to permit the armature to break away from the associated working contact before relay 24 has had time to operate, except under the special conditions of an intentional break in the line for the purpose of placing the selector under the control of the line relay, as will now be described.

Operating the signal-station selectors It will now be assumed that the attendant or dispatcher at the telegraph transmitting station desires to signal the attendantat one of the signal stations along the telegraph line. In order to condition the selectors Sl and S2 for control over the telegraph line, the dispatcher causes the operation of the telegraph transmitter to cease and he opens the telegraph line at the pushbutton 4 for a period of several seconds (ten for example), after which he closes the line by permitting the key 4 to restore. He then sends two desired series of impulses over the line by successive operations of the calling device CD.

In the signal station A, when the line is opened places a shunt around the Winding of slow-acting release relay 22. After a short interval, relay 22 restores and closes an operating circuit for timer relay 23, whereupon the armature of relay 23 strikes its cooperating Contact and thereby sets4 the associated spring into vibration controlled by Weight 37. As soon as the vibratory motion of the spring contact has ceased, (after a period of about three seconds), lock relay 24 operates and closes a locking circuit for itself in series with cut-in relay 25, which locking circuit includes the inner contacts of cut-out relay 29. Relay 25 does not operate in the locking circuit of lock relay 24 for the time being because relay 25 is shunted by the initial circuit established for relay 24 through the contacts of relay 23.

The relays remain in this condition (with relays 2| and 22 restored, and with relays 23 and 24 operated) until the push-button 4 at the transmitting station is restored to permit current to flow again over the telegraph line, whereupon relays 2| and 22 reoperate, and relay 23 restores.

relay 2.5' now A.operates series witli-,loelslnere- `lay 24 and through .the inner contacts oi out-'out 1,elay29`- Upon operating. out-.in relay l25 opens a point in the -oirouit of release-magnet .33 atits lower armature, at the saine .time.preparing to extend yground potential to the wiper `38 of lthe switch rneohanism- At its upper armature relay, disconnects the armature off line relay 2 lfrom the junction of resistor nand relay 22, and ex-L tends it through olf-normal contats and vertioal-series relay 36 vto the vertical magnet 1.3 I preparatory to the ,operation of theseletor;

With cut-in relay 25 now operated `n theflockine oirouit of relay .24, line relay .2| is new. flisassoeiated from relays '22 and 23 and .isl lniassociation with the mechanism of the selector so as to enable the selector to respond to control impulses transmitted over the line. -r Y' As vpreviously stated, th ,dispatcher` at the transmitting station now dials two digits, which operation. it will be understood, Consists in plao.- ine his nger inthe finger hole of thefdlal .oorresponding to the number of impulses desired in the first digit; turning the diajlaround to stop a position; and releasing the .dial andper-nutting it to return to normal vposition by. springA action,`

' following which he repeats the operation for the second desired digit.

When the first digit is dialled, the Anormally closed impulse contacts of the calling device?, are separated a number of times depending upon the Value of the digit. Each time the contacts are separated, line relay 2| at signal station VA is momentarily restored.

Each time line relay 12| is `restored (under the circuit conditions now existing), a circuit :is closed through contacts of the .operated cut-in relay 25, off-normal vcontacts 35, vertical series relay 26, and through vertical magnet 3| to the ungrounded pole of the local battery. The vertical magnet 3| operates lto raise the wiper 38 opposite the level of contacts corresponding to the digit dialled. Vertical-series relay22 is op'- erated upon the delivery oftherst impulse to the Vertical magnet and prepares-a holding circuit for itself which serves to maintain its own circuit and that of the vertical magnet intact after 01T- normal contacts 35 have shifted, as they doupon the first vertical step of the switch. Also, `offnormal contact 36 prepare a circuit for cut-out relay 29, and oir-normal contacts 34 preparefa circuit for release magnet 33. l

At the end of the series of impulses, vertical series relay 26 restores and transfers the operati ing circuit `from vertical magnet 3| to rotary magnet 32.

When the next series of impulses isdeIiVered, each resulting restoration of line relay 2| results in the transmission of an impulse through` the now-shifted olf-normal contact combination 35, contacts of the now-restored vertical series relay 26, and through slow-acting rotary-series relay 21 to rotary magnet 32. Magnet 32 is therefore operated to cause wiper 38 to be rotated into engagement with the desired contacts in the selected level.

When rotary series relay 21 operates it closes a circuit for locking relay 28. Locking relay 28 thereupon operates and closes a locking circuit for itself in series with cut-out relay 29, through the now-closed off-normal contacts 36. Cut-out relay 29 does not operate for the time being because it is short circuited by the initial application of ground potential to the winding of locking relay 28 at the upper contacts of relay 21.

et the-'end tlieseries, of rotary .impulses sloweaotins-rotary ,series Arelay 21 restores. and opens tlleinitial oi Uit ofrelay 28f Relay .2B now renlains opery .teu its looting oireuit through. y:29, .and relay 2.9 operates Upon operating, relsy-29 .applies vground potential to wiper at its lower ,Conteo-ts. ouen the lower armature-ofthe still operated eux-1n relay 25. .At the same time, cut-out relay ,2,9 opens the lockins o i-rouit throught-he windings of relays 25 and 24.119 .per-Init thesefrelays to restore Relay 25 is slowinrestorine, and therefore maintains wiper `:ity grounded through .contacts of relay ,29 for a substantial fraction of` a second in order that an eective rimpulse be delivered through rvwiper 38 to a selected signa-,1, jin case the wiper of this selector` has :been positioned on va Contact with which a signal-is associated.

When relay 24 restores, Iwhich occurs prior to the'restoration of relay`25 because of the relatively stiff radjustmentpofrelay :24 compared to the adjustment ofv relay 25,' it opens a further point inthe previously .existing locking circuit of the two relays. f

Whenrelay 25 restores, it .disconnects ground potential from wiper138 so as to preventqthe in: advertent grounding of signal `contacts over which this wiper may -passin Irestoring -to normal position., Relay 2 5 also transfers the armature of line relay 2| back to the timing relays v2-2 and `23 at itsi-ipper armature,- while at the normally closed contacts associated with its lower armature it closes a circuit through oir-normal ,contacts 34 for release -magnet 3.3. By the operation of release magnet 33, the wiper 38 is caused to restore to its normal position and the off-normal contacts 34, 35, and 36 return to the normal conditionillustrated--in the drawing.` At off-normal contacts 34:,:thecircuit of release magnet 33 isl opened, while at vonf-normal contacts 36 cthe cir--y cuit .of relays 28 and 29 is 4opened topermit these' relays torestore: The selector Si is now resto-red to'normal position-and is also removed from kunder control of line relay 2| by the .described restoration of relay 25. It will' be liinderstood, of course, that somev contactsin thefbank of the switch Sl are connected to signals, while non-corresponding bank contacts inthe Abank `o1" lthe switch S2 are con-l1l nected to signalsfat :signal station C. As many sig-nais as 'desired may ybeprovided at either signal station, within the limits of the capacity of' the' selectors. By way of illustration, three signals are shown at station A, connected to bank contacts |2, 3, and |4 (corresponding to numbers 12, 13,-and 14 as called from the calling device 3l) It will be understood that the contact bank 39 isl wired by means of `separate conductorsto terminals inthe terminal block 49 which terminals maybe suitably marked to indicate the contacts with-which they lare respectivelyI connected. The signal relays such as 5|, 52, and 53 which are provided at the station are wired to terminals in a block such as 4|, and jumper wires 42 connect the terminals in block 4| to assigned ones o-f the terminals in block 40, according to any desired numbering arrangement.

Assuming now that wiper 38 of the selector Sl has been set on the fourth contact of the first level (in response to dialling the number I4), the momentary application of ground potential to the selected contact which is made as hereinbefore described results in the momentary closure of a circuit over the associated one of the jumper conductors (42) and through the relay 5|. Relay 5I operates and locks' itself through the release push-button 55 and the common signal relay 56. Relay 5| also closes a lighting circuit for the individual signal lamp 54 toznotify the attendant of the identity of the signal relay operated. Relay 56 closes a. circuit through the signal buzzer 51 to call the attendants attention audibly to the fact that a signal has been operated.

After the attendant has taken note of the operated signal, he may restore the signal apparatus to normal condition by momentarily depressing button 55, whereupon relay 56 restores and stops the operation of the buzzer and relay 5I restores and extinguishes the lamps 5l, in addition to opening its previously established locking circuit at an additional point so that the locking circuit does not become reclosed when the button 55 is restored.

By the arrangement illustrated and described, the selector is automatically restored to normal position following the dialling of a desired signal number, with the result that the dispatcher at the transmitting station may (by reoperation of push-button 4), dial vseveral numbers successively, each indicative of a desired signal operation, and the selector S will respond to each of the numbers torbring its Wiper 38 into engagement with the corresponding contact, and the similar selector S2 at signal station B does likewise. Then, the special signalling operations being completed, the dispatcher at the transmitting station may permit the telegraph transmitter to proceed with the transmission of telegraph messages without further response of the selectors.

- What .is claimed is:

1. In combination, a line extending between a transmitting station and a receiving station, a selecting device associatedwith said line and located between the transmitting station and the receiving station, means for transmitting signals comprising codes of impulses over the line, said device normally being out from under the i control of signals transmitted over the line, timing means associated with the selecting device, means for transmitting a special signal of the same character as but of a length not encoun- V:tered in ordinary transmission over the line, said timing means responsive only to said special signal for placing said selector under the control of the line at the termination of the said special signal, said selector thereafter responsive to signals over the line.

2. In combination, a line of the normallyclosed-circuit type having means associatedtherewith for transmitting messages thereover by opening and closing the line to send telegraphic signals, means for sending signals having a special significance over said line, a responding device controlled-.over the line by said special signals,

said responding device being normally out from under the control of the line, means responsive only to a prolonged cessation of current flow over the line preceding the transmission of special signals for placing said device under the control of the line, and means automatically responsive to the operation of said device by said special signals for again removing it from under the control of the line.

3. In combination, a line, a signal station located along said line, a selector at said signal station having a group of contacts, means for sending messages over said line without affecting said selector, a. timing device controlled over the line, means controlled by said timing device responsive to a prolonged cessation of current flow over the line for actuating said timing device to bring said selector under the control of the line, means for transmitting selector actuating signals to cause said selector to select a desired contact, and means automatically eiective after the selector has selected a contact for removing it from under the control of the line.

4. In combination, a line extending between a transmitting station and a receiving station, a selecting device associated with said line and located Abetween the transmitting station and the receiving station, said device normally being out from under the control of signals transmitted over the line, timing means associated with the selecting device responsive to signals as transmitted over said line, means effective when a special signal of a length not encountered in ordinary transmission is transmitted over the line for placing said selector under the control of the line at the termination of. the said special signal, means for operating said selector responsive to selecting signals thereafter received over the line, and means automatically effective after the selector is operated for removing said selector from under the control of the line.

5. In combination, a line extending between a transmitting station and a receiving station, a selecting device associated with said line and located between the Vtransmitting station and the receiving station, said device normally being out from under the control of signals transmitted over the line, timing means associated with the selecting device responsive to signals as transmitted over said line, means effective when a special signal of a length not encountered in ordinary transmission is transmitted over the line for placing said selector under the control of the line at the termination of the said special signal, means for operating said selector responsive to selecting signals thereafter received over the line, and means automatically eiective after the selector is operated for restoring said selector to normal position.

1 CLARENCE E. LOMAX. 

